Conventionally, for example, as disclosed in Patent Literature 1 and Patent Literature 2, an oil supply system that supplies engine oil (lubricating oil) to a portion to be lubricated or a portion to be cooled is provided in an engine (internal combustion engine). Also, an oil jet apparatus is connected to the oil supply system. Then, part of the engine oil discharged from an oil pump is supplied to the oil jet apparatus and injected to the rear surface side of pistons (hereinafter, this oil injection is referred to as an oil jet). The pistons are cooled by the oil jet, and for example, the occurrence of knocking can be prevented.
Also, a valve mechanism that adjusts the amount of the oil jet or switches the execution and stoppage of the oil jet is provided in the oil jet apparatus disclosed in the above-mentioned patent literatures. Specifically, a valve body that is freely movable forward and backward with respect to an oil path connected to an oil jet nozzle is provided in the valve mechanism. An energized force from a spring is applied to the valve body, and the position of the valve body is adjusted by switching the excitation and non-excitation of an electromagnetic solenoid, thereby changing the opening area of the oil path.